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Fuel pump lever arms and what they mean for flow.
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   Forward Look Technical Discussions -> Engine, Exhaust, Fuel and IgnitionMessage format
 
56D500boy
Posted 2019-06-17 6:34 PM (#583597)
Subject: Fuel pump lever arms and what they mean for flow.



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I had an Audi parts garage sale and purge on the weekend to free up some shelf space for my 56 Dodge parts. I've spent most of the morning and the afternoon out in the garage sorting through the parts and organizing them.

In doing so, I found my fuel pump (FP) box that contained the FP I took off the car when I got it in Sept. 2016 and a new in box Airtex 4280 FP. They are pretty much identical including the length of the lever arm. For some reason, I am running a new old stock 4280 FP that has a shorter lever arm, I guess because I bought it from a knowledgeable Chrysler 300 owner/tuner. Based on this photo that I annotated before (for a fuel pump thread), I am wondering if the shorter arm NOS 4280 isn't providing enough fuel at higher speeds (the car seems to "hit the wall" at 70-75 indicated mph). Hmm....

Previous thread: http://www.forwardlook.net/forums/forums/thread-view.asp?tid=48369&...

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ronbo97
Posted 2019-06-17 8:59 PM (#583603 - in reply to #583597)
Subject: RE: Fuel pump lever arms and what they mean for flow.


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56D500boy - 2019-06-17 6:34 PM . I am wondering if the shorter arm NOS 4280 isn't providing enough fuel at higher speeds (the car seems to "hit the wall" at 70-75 indicated mph).

I had a similar experience with my 58 Plymouth. Around the same speeds, it seemed to be holding back a bit. I had my distributor rebuilt by my friend, who has an old tyme distributor machine. He found that the shaft was wobbly and had a few other problems. He flawlessly rebuilt it and demonstrated the improvement at simulated high speeds, on the machine. Now the Plymouth accelerates nicely past 70. I had it up to about 85 before letting off the gas. The car is very happy.

Ron

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wayfarer
Posted 2019-06-20 12:24 PM (#583777 - in reply to #583597)
Subject: Re: Fuel pump lever arms and what they mean for flow.



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The overall length of the arm has nothing to do with pump operation. The pump is mounted in a fixed location and operated by an eccentric also in a fixed location.
Now, the shape of the arm is a different story and can/will affect operation if it sits too low in relation to the eccentric.
Place one of your pumps on the edge of your workbench and draw a line around the arm, then sit the next one on the same spot and compare arms.
Use the mounting bolt hole to note pump location. Also, if they have been used, note the location of the wear patch from the eccentric.
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normsclassicradio
Posted 2019-06-20 5:01 PM (#583801 - in reply to #583597)
Subject: Re: Fuel pump lever arms and what they mean for flow.



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Notice in the photo the NOS one. The arm is higher in relation to the mounting holes. More stroke?
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